Tracer mechanism for machine tools



June 21, 1949. E. E. HALLBERG ET L TRACER MECHANISM FOR MACHINE TOOLS 2Sheets-Sheet 1 Filed Nov. 3, 1944 INVENTORS. 9

Jake 7W e715 Filed Nov. 3, 1944 Jun21,1949. a E. HALLBERG EAL 2,473,584

TRACER MECHANISM FOR MACHINE TOOLS 2 Sheets-Sheet 2 six k 44 {F j 1 /3351 .57

' J I I INVENTOR5. jzzzfljifla/e y Patented June 21, 1949 2,473,584TRACER MECHANISM FOR MACHINE 'rooLs Elmer E. Hallberg and Joseph C.Verstynen, Rockford, Ill., assignors to Rockford Machine Tool Company,Rockford, Ill., a corporation of Illinois Application November 3, 1944,Serial No. 561,762

' 14 Claims. (01. 90-243) This invention relates to machine toolsequipped with pattern controlled mechanism governing the movement of thecutting tool.

It is a general object of the invention to provide a new and improvedtracer mechanism for a pattern controlled machine tool.

Another object of the invention is to provide a new and improvedhydraulic circuit and tracer mechanism included therein for actuatingthe adjustment of a cutting tool in a direction transverse to therelative movement between the tool and the work.

More particularly it is an object of the invention to provide a tracercontrolled mechanism for adjusting a cutting tool including meansresponsive to movements of the tracer for avoiding unduly rapid changesof position in the cutting too1 so as to prevent chattering thereof.

More specifically, the invention includes improvements in hydraulicallyactuated tracer controlled mechanism whereby the hydraulic pressureapplied for moving the cutting tool toward the work is automaticallymodified in accordance with the rate of change of position of thetracer.

Other objects and advantages will appear from the following descriptiontaken in connection with the drawings, in which Fig. 1 is a diagrammaticview showing the essential parts of a machine tool embodying theinvention, and including a cutting tool, a tracer mechanism, and ahydraulic circuit through which the tracer actuates the tool.

Fig. 2 is an elevational view showing a valve actuating lever with atracer mechanism controlling it and with a stabilizing device embodyingthis invention applied thereto.

While the invention is susceptible of various modifications andalternative constructions, it is shown in the drawings and hereindescribed in a preferred embodiment. However, it is not intended thatthe invention be limited to the specific disclosures made, but rather itis the intention to cover all modifications and alternative structuresfalling within the spirit and scope of the invention as defined in theappended claims.

The specific structure shown in the drawings may be understood asincluding a valve quite similar to that disclosed in Patent No.2,311,987,

issued to Paul S. Jackson, February 23, 1943.

This valve includes a fixed sleeve and a cylinder rotatably adjustablein the sleeve for registering ports in the cylinder with ports in thesleeve to control the flow of pressure fluid for actuating the cuttingtool of a machine.

The valve is employed in connection with a cylinder and piston devicearranged to shift the cutting tool toward or from the work, and thevalve acts as a reversing valve in that it is arranged to directpressure fluid into one end of the cylinder or into the opposite endthereof, depending upon whether the valve itself is shifted in onedirection or the other from a normal neutral position by a correspondingmovement of a pattern-controlled tracer. Since the valve and itsoperating tracer are mounted on the same support as the tool, while thetracer is actuated by a pattern carried on the same support as the workpiece, the range of movement of the valve and tracer in either directionfrom their neutral position is usually rather limited because eachmovement of the tracer and valve results almost instantly inacorresponding adjustment of the tool support, carrying the valve bodilywith it and restoring thenormal neutral position of the valve andtracer. However, if the pattern includes a part which is quite steeplyinclined to the direction of feed, the valve will be shifted morerapidly than usual, attaining an opening which tends to apply excessivepressure to the tool before the resulting adjustment of the tool supportbegins to modify the position of the valve. The present inventionincludes means for temporarily reducing the effective pressure availablefor shifting the tool whenever movement of the tracer and consequentopening of the tracer-operated valve exceeds a predetermined range fromthe neutral position of these parts.

Fig. l represents the valve diagrammatically at l with a pressure line 2leading from a pump 3 actuated by a motor 4 for maintaining a constantsupply of oil or other pressure fluid drawn from a tank 5. Fig. 1includes at I a projected end view of the valve cylinder I with itsactuating rock shaft 6 and lever arm I. Movement of the arm I up or downshifts the cylindrical valve at l to admit the pressure fluid to acylinder 8 having a piston 9 connected by a, piston rod ID to the toolcarriage II for raising or lowering the cutting tool l2 carried thereby.If the valve admits fluid to the conduit l3 leading to the lower end ofthe cylinder 8 the tool l2 will be raised and if the valve l is shiftedto admit the pressure through the line [4 to the upper end of thecylinder 8 the tool l2 will be lowered.

The effective pressure supplied through the conduit 2 is regulated by apressure relief valve l5 connected through a drain conduit IE to thetank 5; and liquid expelled from either end of the cylinder 8 bymovement of the piston is regreater 3 turned through the valve 9 to thetank by way of a return conduit I? which includes the back pressurevalve 18 operating in a well understood manner.

For purposes of illustration, this invention is shown herein as appliedto a machine of the planer type in which a work piece 28 and a pattern2i are mounted in fixed relation to each other so as to have similarmovements relative to the cutting tool i2 and tracer finger 22,respectively. The cutting tool 52 and the tracer mechanism are-bothmounted on the tool carriage which is customarily fixed in a machine ofthis type. while the bed or table ti supporting the work piece as andpattern 2i travels horizontally in alternate cutting and return strokes.The in.- vention is equally applicable, however, to a machine in whichthese relations are reversed so that the work piece and pattern arestationary, while the tool carriage ii is arranged to travel over them.

As shown in Fig. 2 the tracer point or finger 22 is slidably mounted forvertical movement in a guide frame 23 which is attached to the end wallor head 2d of the casing enclosing the valve i. The lower end of thefinger 22 normally rests upon the upper surface of the pattern 2i, asshown in Fig. 1, while the rounded upper end 22 of the finger engagesthe lever arm '5 on the end of the valve shaft 6. A small cylinder 25 isdisposed above the lever arm l and contains a piston 26 having a pistonrod 2i! which bears against the upper side of the lever l for holdingthe lever constantly in engagement with the upper end of the tracerfinger 22 and holding the tracer finger in contact with the pattern 2i.A relatively light pressure normally about nine-pounds per square inchis maintained by an auxiliary pump .28 which is supplied through aconduit 29 tothe upper end of the cylinder 25. Any leakage of pressurefluid past the piston 28 returns to the tank by way of a drainpipe 3d,and the pressure supplied through the conduit 29 is controlled by aregulating valve 3| connected as shown in Fig. l. The valve 3| thusprovides a yielding means for holding the tracer finger to the pattern,since whenever the tracer finger is moved upward it must overcome thenine-pound pressure in the line 29, backing up the fluid therein pastthe regulating valve 3!.

The guide 23 includes a cylinder 3 containing a piston 34 which has apiston rod 35 equipped with an adjustable head 36 for engaging the valveactuating arm 1 as shown in Fig. 2. Pressure fluid supplied through thepipe 31 maybe admitted at will to shift to the cylinder 33 the valve lin a direction for lifting the tool i2 from the work independently ofthe tracer finger 22. This may be accomplished by the operator byactuation of a manual control valve 38 whenever it is desired to raisethe tool from the work or it may be effected automatically at the end ofthe working stroke to permit rapid return of the table and for thatpurpose any suitable trip operated valve, not shown, may be employed. Itis, therefore, convenient to provide the supply of pressure fluidthrough the pipe 31 from the same source as that which supplies pressurefor driving the table in its reciprocating movement, and Fig.1 indicatesa supply pipe 39 and return conduit 40 which may be understood asconnected to such a source.

The tracer valve mechanism shown herein differs somewhat from that ofPatent No. 2,311,987, above mentioned, in that the actuating arm I is dsecured directly and rigidly to the rock shaft 6 of the valve cylinder,and the tracer finger 22 engages the arm 'i directly instead of actingthrough a jointed linkage, as in the patented structure. This insures asensitive response of the valve to movement of the finger 22 andrequires only the relatively light pressure supplied by the piston 26 tomaintain contact of the tracer finger with the pattern. In some cases,however, if the contour of the pattern rises or falls rather abruptly,the resulting rapid opening of the ports of thevalve i may applyexcessive pressure to the piston 9 and to the tool i2 causing the toolto chatter and to produce a relatively rough out. To avoid this result,there is provided a stabilizing mechanism which includes a cylinder orvalve casing li secured to the head or end wall of the valve i andcontaining a spool-type valve member 62 with a valve stem d3 extendingtherefrom,

and provided with an adjustably fitted flanged head M. A short arm 35having a rounded end 36 extends rigidly from the hub of the valveactuating lever "i with its said rounded end portion at engaged betweenthe flanges ll and 38 of the head it on the valve stem 63. With thelever arm 'i at its normal neutral position the middle portion or spoolof the valve 42 closes the ports 5! and 52 which are connected by pipes53 and 5 with the conduits i3 and i l, respectively. The ports 5! and 52are in circumferential alignment so that shiftingof the valve member 32in the cylinder 3i will provide a connection between these ports by wayof the annular groove 55 or the annular groove 56, depending upon whichway the valve 42 is shifted from its normal position. The connectionbetween the ports 5i and 52 operates as a. shunt across the lines i3 andM thus providing for a partial return flow of the pressure liquid fromone of these lines to the other and diminishing the effective pressureoperating against the piston 9 for moving the tool ii.

To. permit normal operation of the valve i within a limited range ofmovement of the tracer finger 22, either above or below its neutralposition, the spool of the valve 62 which closes the ports 5! and 52 ismade slightly wider than said port so as to lap them in both directionsof its movement. This lap must be about .005 of an inch in eachdirection. The corresponding normal range of the tracer finger 22 andthe lever 1 may be further increased by fitting the rounded end 46 ofthe arm 45 with clearance between the flanges ll and 48; preferably,such clearance is about .005 of an inch at each side of the part 36.Thus, the arm I must be swung far enough to shift the part 46 about .010of an inch before the stabilizer valve 42 will begin to open the ports5| and 52 so as to lower the effective pressure operating upon the tooll2, and since the arm 45 is considerably shorter than the effectivelength of the arm I with which the tracer finger 22 is engaged, thetracer will have a range of something more than .010 of an inch ineither direction from its normal neutral position. The stabilizer valve42 is normally supported upon a light spring 51 which holds the spoolportion of the valve centered with respect to the ports 5| and 52, thatis, lapping beyond said ports above and below them by equal amounts. Thehead 44 is adjustably secured on the valv stem 43 between nuts 58 and 59so that with the valve at this normal position the flanges 41 and 48 maybe spaced with equal clearance from the part 46 when the lever arm 1holds the valve i in its normal neutral position. Any leakage ofpressure fluid past the valve 42 is drained from the valve chamber llthrough a pipe Ill leading to the tank 5.

since, as indicated by the outlines III in Fig. 1. the tracer valve I iscarried on the same support as the tool l2 and moves bodily up or downwhen the tool is shifted by hydraulic pressure in the cylinder 8, thetracer flnger 22 will not usually move far from its normal neutralposition in following a pattern because a slight movement of the tracerfrom this neutral position actuates the piston 9 to shift the support 60and the tool l2 in the same direction by a corresponding amount. Thismovement of the support 60 of course carries with it the casing of thetracer valve l and this bodily movement of the tracer valve relative tothe tracer finger 22 which is held against the pattern produces areverse swing of the lever arm 1 which readiusts the valve to its normalneutral position. The tracer control of the tool I2 is thus sufllcientlysensitive to cause the tool to respond accurately and smoothly togradual inclinations of the pattern without resulting in any movement ofthe tracer beyond its normal range within which the stabilizer valve 42is affected; but, whenever the pattern involves an unusually steepportion requiring the tracer to move rapidly in either direction infollowing this portion of the pattern the resulting excessive movementof the lever 1 will take up the clearance between the part 46 and one ofthe flanges of the head 44 and will then shift the spool portion of thevalve 42 far enough to provide communication between the parts 5| and 52and between the lines l3 and II as already described. This lowering ofthe effective pressure operative upon the piston 9 will prevent the tooll2 from being too forcibly fed into the work piece and will permit it tocontinue cutting smoothly instead of chattering under excessivepressure.

To insure smooth operation of the tracer finger 22 in the guide 23 thefinger is formed with a reduced portion 22 adapted to contain anddistribute lubricant along the guide surface as the finger movestherein. To insure accurate positioning of the head 36 on the stem 35 ofthe auxiliary tool lift device, the head 36 is threaded onto the end ofthe stem 35 and secured at adjusted position by means of a lock nut 36on said stem.

In the tracer valve shown in Patent No. 2,311,- 987, above mentioned,the ports of one member of the valve are so arranged as to be completelyout of registration with the ports of the other member when the valve isin neutral position, so that communication is cut off between the supplyof pressure fluid and both conduits leading to the cylinder and pistondevice which shifts the tool. It may be understood, however, that theports of the valve may be so designed that in neutral position the portsleading from the pressure fluid supply will slightly overlap the portsconnecting with both conduits leading respectively to the opposite endsof the cylinder. This will tend to afiord a still more sensitiveresponse to movement of the tracer, the piston of the tool adjustingdevice being confined between the two opposing columns of, pressurefluid and moving instantly in response to any differential of pressureas between the two. The stabilizing device herein shown and describedwill be equally effective and advantageou whether the tracer valve isconstructed exactly in accordance with said Patent No. 2,311,987 or withoverlapping ports as just explained.

We claim as our invention:

1. In a machine tool having a pair of relatively movable slides with atool and tracer carried by one slide and a work-piece and patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a valve with conduitsleadin therefrom to opposite ends of the cylinder, respectively, saidvalve being movable in response to the tracer in either direction from aneutral position for directing pressure fluid selectively to one end ofthe cylinder or to its opposite end, by-pass means operableautomatically to reduce the effective pressure applied to the cylinder,and means connected to the tracer-operated valve effective to actuatesaid by-pass means when the movement of the tracer-operated valveexceeds a predetermined range from its neutral position.

2. In a machine tool having a pair of relatively movable slides with atool and a tracer carried by one slide and a work piece and a patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a valve operable by thetracer, conduits connecting said valve to opposite ends of the cylinder,respectively, said valve being movable in either direction from aneutral position for directing pressure fluid selectively to one end ofthe cylinder or to its opposite end, means forming a passage connectingsaid conduits together at points intermediate the tracer valve and saidcylinder, a normally closed stabilizer valve interposed in said passage,and means shifting said stabilizer valve to open position when themovement of the tracer-operated valve exceeds a predetermined range fromits neutral position.

3. In a machine tool having a pair of relatively movable slides with atool and a tracer carried by one slide and a work piece and a patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a valve operable by thetracer, conduits connecting said valve to opposite ends of the cylinder,respectively, and through which pressure fluid is admitted to thecylinder under control of said valve, a, normally closed stabilizervalve interposed in a passage connecting said conduits intermediate thetracer valve and said cylinder, and a lost motion connection betweensaid tracer and the stabilizer valve operable to shift the latter toopen position when the movement of the tracer exceeds a predeterminedamount.

4. In a machine tool having a pair of relatively movable slides witha-tool and a tracer carried by one slide and a work piece and a patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a valve operable by thetracer, conduits connecting said valve to opposite ends of the cylinder,respectively, and through either of which pressure fluid may be admittedto one end of the cylinder while pressure fluid is released from theother end of the cylinder through the other conduit under control ofsaid valve, and means automatically providing a restricted connectionbetween said conduits independently of said valve when the movement ofthe'tracer exceeds a predetermined amount from its neutral position.

5. In a machine tool having a pair of relatively movable slides with atool and a tracer carried by one slide and a work piece and a patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a reversing valve operableby the tracer in either direction from a neutral position, conduitsconnecting said valve to opposite ends of the cylinder, respectively,and through either of which pressure fluid may be admitted to thecorresponding end of the cylinder while ressure fluid is released fromthe other end of he cylinder through the other conduit under control ofsaid valve, a normally closed. stabilizer valve interposed in a passageconnecting said conduits at points intermediate the tracer valve andsaid cylinder, and means shifting said stabilizer valve to open positionwhen the movement of the tracer-operated valve exceeds a predeterminedrange from its neutral position.

6. In a machine tool having a pair of re1atively movable slides with atool and a tracer carried by one slide and a work piece and a patterncarried by the other slide, a cylinder and piston device operable tomove the tool slide toward and from the work, a tracer valve operable inresponse to the tracer in either direction froma neutral position,conduits connecting said valve to opposite ends of the cylinder,respectively, and through either of which pressure fluid may be admittedto one end of the cylinder while pressure fluid is released from theother end of the cylinder through the other conduit under control ofsaid valve, a normally closed stabilizer valve interposed in a passageconnecting said conduits intermediate the tracer valve and saidcylinder, and means shiftin said stabilizer valve to open position whenthe movement of the tracer valve exceeds a predetermined range from itsneutral position, said stabilizer valve controlling ports into whichsaid passage is connected and being formed to lap said ports in bothdirections from its normal closed position whereby said valve must beshifted a limited distance before it opens the passage between saidconduits.

7. In a machine tool having one support with a cutting tool and a tracercarried thereby, another support with a work piece and a pattern carriedthereon, said supports being relatively movable to cause the tool totraverse the work in the cutting operation and to cause the tracer totraverse the pattern, and a fluid pressure controlled mechanism forshifting the tool transversely of the direction of said traverse inresponse to similar transverse movements of the tracer in traversing thepattern including a valve operable by the tracer and controlling theadmission of pressure fluid to said mechanism, bypass means operableautomatically to reduce the effective pressure applied to said.mechanism, and

means connected to the tracer-operated valve efiective to actuate saidby-pass means when the pattern-controlled movement of the tracer exceedsa predetermined amount.

8. In a machine tool havin one support with a cutting tool and a tracercarried thereby, another support with a work piece and a pattern carriedthereon, said supports being relatively movable to cause the tool totraverse the work in the cutting operation and to cause the tracer totraverse the pattern, and a fluid pressure controlled mechanism forShifting the tool transversely of the direction of said traverse inresponse to similar transverse movements of the tracer in traversing thepattern including a valve operable by the tracer and controlling theadmissionof pressure fluid to said mechanism, fluid supply and returnconduits for said mechanism, means forming a passage connecting saidconduits, a normally closed stabilizer valve interposed in said passageconnecting said conduits, and means shifting said stabilizer valve toopen position when the pattern-controlled movement of the tracer exceedsa predetermined amount.

9. In the combination defined in claim 8, said stabilizer valve being ofthe spool type connected to the tracer and movable in a cylindricalcasing having circumferentially aligned ports leading into said passage,and the spool of the valve having a limited lap with respect to saidports in both directions of valve movement, whereby effective opening ofthe passage is delayed until the tracer movement exceeds saidpredetermined amount.

10. In amachin tool havin one support with a cutting tool and a tracercarried thereby, another support with a work piece and a pattern carriedthereon, said supports being relatively movable to cause the tool totraverse the work in the cutting operation and to cause the tracer totraverse the pattern, and a fluid pressure controlled mechanism forshiftin the tool transversely of the direction of said traverse inresponse to similar transverse movements of the tracer in traversing thepattern including a valve with a rocker arm operable by the tracer, saidvalve controlling the admission of pressure fluid to said mechanism, andfluid supply-and return conduits for said mechanism, a normally closedstabilizer valve interposed in a passage connecting said conduits, and alost-motion connection between said rocker arm and the stablizer valveoperable to shift the latter to open position when the movement of therocker arm exceeds a predetermined amount.

ii. In a machine tool having one support with a cutting tool and atracer carried thereby, another support with a work piece and a patterncarried thereon, said supports being relatively movable to cause thetool to traverse the work in the cutting operation and to cause thetracer to traverse the pattern, and a fluid pressure controlledmechanism for shifting the tool transversely of the direction of saidtraverse in response to similar transverse movements of the tracer intraversing the pattern including a tracer valve controlling theadmission of pressure fluid to said mechanism, means providing a one-waydrive between the tracer and said valve by which the valve is movable inone direction by the tracer, a fluid pressure actuated member having aoneway operating engagement with said tracer valve arranged to move itin the opposite direction and to maintain contact of the tracer with thepattern, means supplying fluid thereto at a relatively low pressure ascompared with the pressure employed to shift the tool, said lastmentioned means including a supply conduit with a pressure relief valveconnected thereto adapted to yield to permit actuation of the tracervalve by its one-way drive from the tracer.

12. In a machine tool having one support with a cutting tool and atracer carried thereby, ,another support with a work piece and a patterncarried thereon, said supports being relatively movable to cause thetool to traverse the work in thecutting operation and to cause thetracer to traverse the pattern, and a fluid pressure controlledmechanism for shifting the tool transversely of the direction of saidtraverse in response to similar transverse movements of the tracer intraversing the pattern including a valve with a rocker arm operable bythe tracer, said valve controlling the admission of pressure fluid tosaid mechanism, and a fluid pressure operable member engageable withsaid rocker arm and operable to shift the arm independently oi thetracer in a direction for causing the tool to be withdrawn from thework, together with a control valve for supplying pressure fluid foractuation of said member.

13. In a machine tool having one support with a cutting tool and atracer carried thereby, another support with a work piece and a. patterncarried thereon, said supports being relatively movable to cause thetool to traverse the work in the cutting operation and to cause thetracer to traverse the pattern, and a fluid pressure controlledmechanism for shifting the tool transversely of the direction of saidtraverse in response to similar transverse movements of the tracer intraversing the pattern including a valve with a rocker arm, said tracerhaving a one way driving engagement with said rocker arm by which thesaid valve is movable in one direction, a fluid pressure operatedplunger having a one way driving engagement with said rocker armarranged to urge said arm in the opposite direction for maintainingcontact of the tracer with the pattern, a fluid supply line for saidplunger and a relief valve connected to said line permitting the plungerto yield in response to pattern controlled movements of the tracer androcker arm, a fluid pressure operable device having driving engagementwith said rocker arm adapted to move it in opposition to said plungerand to shift the valve into position for applying pressure fluid to saidmechanism to actuate the latter in a direction for withdrawing the toolfrom the work, and a control valve operable independently oi the tracerto apply fluid pressure to said device.

it. in a machine tool having one support with a cutting tool and atracer carried thereby, another support with a work piece and a patterncarried thereon, said supports being relatively movable to cause thetool to traverse the work in the cutting operation and to cause thetracer to traverse the pattern, and a fluid pressure controlledmechanism for shifting the tool transversely of the direction of saidtraverse in response to similar transverse movements of the tracer intraversing the pattern including a rotatably adjustable valve with arocker arm attached thereto and operable by the tracer, said valvecontrolling the admission of pressure fluid to said mechanism, fluidsupply and return conduits for said mechanism, a normally closedstabilizer valve interposed in a passage connecting said conduits, saidvalve having a reciprocabie stem and a second arm attached to therotatable valve and connected to said stem for shifting the stabilizervalve to open position when the m0vemerit of the rotatable valve exceedsa predetermined amount.

ELMER E. HALLBERG. JOSEPH C. VERSTYNEN.

REFERENCES CE'H The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,003,557 Sassen June 4, 19352,025,748 Howe Dec. 31, 1935 2,030,022 Kain Feb. 4, 1936 2,079,720 ShawMay 11, 1937 2,190,988 Johansen Feb. 20, 1940 2,301,719 Turchan Nov. 10,1942 2,349,171 Jackson May 16, 19%

